Method for treatment of barking waste



J1me 1966 T. G. BRANDTS ETAL 3,

METHOD FOR TREATMENT OF BARKING WASTE Filed June 29, 1965 UNBARKEU DRUMS SCREENING BARK/N cOARsE wAsT F/BROUS LESS FRAcT/ON cOARsE FRAcTlON DEWATER/NG sEOONO a cOARsE SEMI-DRY F DISINTEGRAT/NG scREEN/NO wATER FINES DEWATERED (PRODUCT4) BARK/N6 wAsTE FURTHER REs/OuE OR DIS/NTEGRAT/NG MIDDLE FRACTION BARK/N6 WASTE A/R cLAss/F/cAT/ON 1 ROus CORK REs/OuE (PRODUCT 3) FRACTION FURTHER COMB/NED .lfli F/BROus FRACTION WET DIS/NTEGRAT/ON wATER wET SCREEN/N6 (P WOOCD I) (BARK FIBRE) [NVENTORS RODU T PROOucT2 THEODORUS 6. BRANDTS DONALD E. HELLEUR ROBERT M. HOPK/Ns JOSEPH A. LIGHTENBERGER BY KM ATTORNEYS United States Patent 3,254,847 METHOD FOR TREATMENT OF BARKING WASTE Theodorus Gerardus Brandts and Donald Edmund Hel-j leur, GrandMere, Quebec, Robert Montgomery Hopkins, Powell River, British Columbia, and 'Joseph Alois Lichtenberger, GrandMer-e East, Quebec, Canada, assignors to Consolidated Paper (Bahamas) Limited, Nassau, New Providence, Bahamas Filed'June 29, 1965, Ser. No. 473,547 I 20 Claims. (Cl. 241-24) This application is a continuation-impart of application Serial No. 84,282, filed January 23, 1961 which is now abandoned.

The present invention relates to the physical separation of the various components of barking waste such as that stripped from pulp logs in pulp and paper mills.

It is the practice among most manufacturers of wood pulp to try to remove as much bark as possible from their pulp wood. This barking of the wood has led to the production of large quantities of waste material which, generally, has been of little commercial value. However, to dispose of this barking waste while at the same time avoiding pollution of various kinds, many pulp mills and especially those using Wet barking methods, have had to burn this waste at some expense. Mills using dry barking methods can, of course, dispose of their waste by burning somewhat more economically.

It is a main object of the present invention to provide a method of separating this barking waste into individual fractions of some commercial value.

The components of barking waste for the purposes of the present invention can be classified and identified as fibrous and non-fibrous. The fibrous components consist of: pieces or particles of wood, which are dislodged from the woody section of the log during the barking ope-ration; the gross fibrous fraction of the bark, often referred to as the inner bark or phloem; and finally that part of the outer bark or phellem which while somewhat corky in nature still possesses a fibrous structure. The non-fibrous components consist mainly of the scaly outermost parts of the outer bark or bark cork.

As a result of the disintegration phases of the present invention, described below, the components of the barking waste may be classified as follows:

'(a) Stringydibrous component-consisting mainly of the fibrous inner bark.

(b) Wood-splinter component'made up of particles of wood of all sizes.

(c) Fibrous cork-chip component-consisting of a variety of shapes and sizes varying from 1" x A2" to 1/8!! X ]/8!!' (d) Non-fibrous cork-chip componentsimilar in size and shape to (c) above.

(e) Fines and dust component-consisting of particles less than A1" in size and made up of fragments of wood, wood fiber, bark fiber, cork scale, etc.

The present invention separates the above components (a to e) into some or all the following product-fractions with a minimum of size reduction or debris:

(1) Wood fiber productconsisting mainly of fraction (b) above.

(2) Bark fiber product-consisting mainly of fraction (a) and some of (c) above.

ice

(3) Bark cork product-consi-sting of fraction ((1), and

some of (c) above.

(4) Fines and dust product-consisting of component (e) above.

Following such a separation, the user of such product fractions can at his discretion further reduce the material in size and/or further classify it as to size or purity and refine it.

The proportions and nature of the above components in the original barking waste and in the final products 1 to 4 above will vary with such factors as:

(a) Method of barking, e.g., in the tumbling friction method using rotating cylindrical drums (wet or dry) the proportion of wood can be quite high; whereas in high pressure water-jet methods the proportion of wood may be low.

(b) The species of wood, e.g., in balsam fir, spruce, poplar (and to a lesser extent in some of the pines) the inner bark is long and stringy, distinctly fibrous in nature and fairly abundant, whereas in Douglas Fir the fibrous fraction consists of relativelyshort needle-like fibers.

(c) The method by which the pulpwood is transported to the mills, e.g., river-driven wood can lose much of its whole or'outer bark in transit, whereas truck or rail transported wood would have most of its bark intact.

(d) The time of year during which the barking or wood cleaning is being done.

The present invention has ben found to work particularly well with the barking waste from the wet-drum barking of wood species having a stringy-fibrous inner bark e.g., species of spruce, fir and poplar.

Once the barking waste has been separated into the four product-fractions 1 to 4 described above by the method according to the invention, to be described below, we have found that these fractions are very useful as raw materials for a number of end-products. For example, the wood fiber product can be a source of wood for the production of wood pulps, for wood particle boards, etc.; the bark fiber product can be used in the production of insulating wool, oruconverted into a bark pulp and used in such products as insulation board, wrapper, corru-gating medium and roofing papers; the bark cork product has been found useful in the production of cork tiles, cork particle board and as a source of chemicals such as phenolics and waxes; the fines and dust product has been cfound useful as a filler material and as a source of chemicals.

Nearly all the present methods of bark fractionation have been concerned with regulating the moisture of the bark in the range of 20 to 45% (based on the wet weight of the bark). This has been done mainly to take ad vantage of the different resistance the cork and fiber fraction of the bark offer to grinding and pulverizing at these low moisture contents. The use of these known methods, therefore, for processing bark-ing waste derived [from wet methods of barking or from water-driven wood, would require the troublesome and expensive step of drying the waste to these lower moisture contents.

It is therefore a further object of the present invention to eliminate the necessity for drying wet barking waste to low moisture contents in order to effect a component separation.

Patented June 7, 1966 In their attempt to make a fraction separation, previous methods tend to reduce the bark to a fine particle size. The present invention makes it possible to obtain fractions having large particle sizes. Such large particle sizes are very desirable in certain end-products, e.g., large cork chips for cork tiles. Smaller particle sizes can be more effectively obtained by further disintegration after fraction separation.

Most of the known methods also relate only to the bark; they do not deal with the actual commercial material commonly referred to as barking waste, which in addition to containing bark can also contain a substantial amount of wood. The presence of this wood gives rise to serious practical problems. Many of these known methods also deal with Douglas Fir bark which is markedly different from the bark of such wood species as spruce, fir, poplar and some of the pines.

It is therefore a further object of the present invention to deal with the utilization of a commercial by-product material called barking waste; and specifically, to deal with the barking waste from those wood species having a stringy-fibrous inner bark, e.g., species of spruce, fir and poplar.

The accompanying drawing is a block diagram showing all the possible steps in the process according to the present invention.

As shown in the drawing, these steps include: a dewatering and coarse disintegration of the barking waste; a further disintegration of the dewatered barking waste; a semi-dry screening of the further disintegrated material to yield a rejected coarse fibrous fraction consisting of stringy-fibrous bark and some Wood and a less coarse accepted fraction; a second, semi-dry screening of the less coarse accepted fraction to yield an accepted fines and dust product consisting of particles of wood, wood fiber, bark fiber, bark cork and scale and a rejected middle fraction consisting of larger wood and bark particles; an air classification of the rejected middle fraction to yield a bark product consisting mainly of bark-cork chips and a fibrous fraction consisting mainly of wood splinters and bark and wood fiber; combining this fibrous fraction from the air classification (consisting of Wood splinters and bark fibers) with the rejected coarse fibrous fraction of the first semi-dry screening step; disintegrating this combined fraction such that the bark fiber only (and, not the wood) is fiberized; wet screening this disintegrated combined fraction to yield a bark pulp product consisting mainly of bark fiber and a wood product consisting mainly of particles of wood and wood fiber. Certain of the above steps can be omitted in some circumstances as will be discussed below.

The operational steps just described serve to convert the barking waste into the four main product-fractions previously mentioned (and numbered above as products 1 to 4). The fibrous woody material rejected by the wet screening constitutes the wood fiber product (product 1); the bark pulp accepted by the wet screening constitutes the bark fiber product (product 2); the bark-cork chip fraction from the air classification step constitutes the bark-cork product (product 3); the fine debris accepted by the second semi-dry screening step, constitutes the fines and dust product (product 4). These productfractions can then be converted into useful end products. Examples of these end-products have already been given above.

The importance of each of the operational steps described, together with the manner in which each should be carried out, will now be described in greater detail. For orientation as to the sequence of the various operational steps, to be described below, reference to the above outline or the drawing may be useful.

The dewatering and coarse disintegration step is desirable when the barking waste consists of very large pieces of stringy bark (or wood) and the moisture content of the barking waste is above 70% (wet bark basis),

generally in the range of -85%. The dewatering step is conveniently carried out in equipment which disintegrates the bark at the same time that it dewaters it. Bark presses similar to the well-known Stacom (trademark of Stacom Industries, Inc.) Press are examples of such equipment. Where the moisture content is below 70%, and very few large pieces of bark and wood are present, this step (or steps) may, of course, be omitted. Where the moisture content is below 70% and many large pieces are present, it may be necessary only to use equipment capable of a coarse size reduction. Many types of such equipment are available on the market. In some cases it may be desirable to separate the dewatering and coarse disintegration steps. This will depend somewhat on the type and the costs of the required equipment available on the market and generally, it will be immaterial which step is performed first. In any of these cases, it is desirable to reduce the moisture content to some level below 70% (e.g., 68-65%, or lower) and to reduce the large pieces of barking waste into pieces not longer than 8-12" in length or shorter than a few inches. The purpose of the first requirement will be discussed later. The purpose of the second requirement, i.e., size reduction, is mainly to convert the barking waste into a physical form which is capable of being fed into the equipment which will carry out the next operational step namely further disintegration. Where this equipment is capable of receiving large pieces of barking waste, then, of course, this step of initial disintegration will be unnecessary.

The purpose of the further disintegration step, possibly more aptly called a disentangling or 'disassociating step, is to break up the non-fibrous bark fraction and to loosen it from the fibrous bark fraction such that each is capable of moving independently of the other, except for mere physical entanglement, and to do these two things in such a way that the fibrous bark components are not reduced in length to any appreciable degree but are merely shredded into as long and stringy a structure as is possible. It is very desirable to maximize the physical entanglement of the fibrous fraction so that on screening, the non fibrous fraction only will be free to pass through the screen. The differences in the gross structure and in the friability and flexibility of the fractions make this objective possible. However, to achieve this objective, care 'must be given to the selection of equipment and to the method of its operation.

Fortunately there is a fairly wide range of moistures at which this further disintegration can be carried out. At the wet end the moisture content can be as high as the dripping wet level (i.e., -85%), but for purposes of traction separation in later steps it should preferably not be higher than 70%; at the dry end it should preferably not be less than 20-30%. The reasons for this are that if it is too wet the non-fibrous bark fraction will not separate from the fibrous bark fraction in subsequent stages, but will tend to stick to it; if it is too dry the fibrous fraction will become too brittle and will tend to break up into smaller pieces and the over-all objective Will be defeated. Generally, a moisture content of 45% or more will in most cases avoid brittleness and breaking up into small pieces. In some cases, less than this amount is usable. 'For the best fiber-cork separation for spruce-balsam type barking waste, a moisture content of approximately 62-63% appears to be optimum. All moisture contents set forth herein are based on the wet material unless otherwise specified.

In the development of this further disintegration step (which is the main disintegration step in the process shown in the drawing of this invention), barking waste from the bar-king operations of several mills was tried. The moisture contents of these wastes was in the order of 8065%, the lower moistures being obtained from those mills using bark'presses. In this range of 8065% moisture, the use of disk attrition mills equipped with plates having concentric rows of projecting spikes, such that the rows of spikes in one disk meshed with those of the other disk, was found to be very effective in achieving the objective mentioned above.

However, since at the higher moisture level there was a tendency for plugging to occur, a satisfactory moisture range for this particular type of equipment is 70-65% (it may be lower, if economically permissible). The size of the feed material should be as stated above, although the particular model of the disk attrition mill used will have some bearing on this.

As has already been suggested the several steps mentioned so far are capable of some variation depending on the type of equipment used and the nature of the barking waste. For example, if the equipment used for the further disintegration step is capable of processing the barking waste as it leaves the barking drums, then the sequence of steps up to the present point may be as follows: a disintegration of the barking waste and, if necessary, a dewatering of the disintegrated barking waste to a moisture content below 70%.

The semi-dry screening steps have as their purpose the division of the disintegrated bark-ing waste preferably into at least three main fractions: one consisting mainly of the coarse stringly-like fibrous component of the bark together with some pieces of wood; one consisting of particles of wood, cork chips, cork scale, and bark fiber (the first three materials being essentially cubic or spheri- =cal in form); and one consisting of a fine debris of woodbark fiber and bark cork. To achieve this three-fraction separation, Le, a coarse, middle and fine fraction, two screening stages are required. .These two semi-dry screening stages are shown in the drawing and are carried out without substantial alteration to the moisture content of the barking waste from the previous disintegrating steps.

To obtain a separation of these three fractions conventional dry or semi-dry screening equipment and techniques can be employed. A screen opening of the order of A, for example, can be used to obtain the coarse fibrous fraction and an opening of the order of /8 to separate the accepted fraction from the A" screen into the other two fractions. Other screen sizes can be used depending on the type of product desired, etc. In the development work two particular types were found effective: a Hummer (trademark of W. S. Tyler Co. of Can. Ltd.) vibrating screen and a trommel or revolving inclined drum screen. The latter .type was found to give particularly good results and was relatively free from blinding. The relatively gentle rolling and tossing action of the trommel prevents the physical disentanglement of the fibrous fraction but still allows the non fibrous fraction to be shaken through the mesh .of the entangled fibers and through the mesh of the screen. One of the preferred methods was to screen the distintegrated barking waste (at a moisture content below 70%) in a trommel equipped with a A" screen and then to screen the accepted fraction from this trommel on a Hummer equipped with a As screen. It was found possible to use the vibrating screen or the trommel for both stages. Both stages could in some cases be set up on one piece of equipment. For example, the screen area towards the inlet could be /8 screen to pass the debris and the area towards the outlet a A" screen to accept the middle fraction and reject the coarse fibrous fraction; a divider on the accepts side between the two screening areas would keep the fine fraction separate from the middle fraction. Operating variable such as: shape and size of screen perforations, spacings, amplitude and rate of vibration or speed of rotation, diameter of drum, angle of incline, length, etc., will depend, within limits, on the type of bark to be separated, the relative amount of inner and outer bark, the moisture content, the amount of wood present, the degree of separation desired, and the actual type of equipment chosen or available. Values for some of these variables can be found in the examples given below. In general, specifications for these variables will depend largely on the tendencies for the fibrous material to blind and in certain cases it may be necessary to use special known techniques to overcome blinding. Air jets, for example, have been found effective. Imparting a vibrating action to a rotating trommel would be effective too in overcoming blinding. I

The air classification step has as its purpose the separation of the bark cork from the middle fraction of the'semidry screening steps. The differences in the specific gravity, size and shape between the various fractions make this purpose possible. The moisture content of the material delivered from the semi-dry screening step prior to the air-classification step need not be substantially altered prior to air classification.

In a typical air classification separator, the material to be treated is caused to flow across the surface of a recip rocating deck. This deck is covered with a porous cover through which air is blown. The air is used to float the material in such a way that it will be stratified, in general the heavier particles settling and the lighter particles rising to the top of the bed. The motion of the separator deck, the volume of the air, the speed of oscillation, and the side and end slopes of the deck all combine to cause the heavier particles to settle and travel further along the deck than the lighter particles. The heavier particles travel along the deck in the direction of its motion and are discharged close to the point end while the lighter particles are floated by the air and travel more or less across the line of motion of the deck and are discharged at the broad end. It has been found in practice that the size and shape of the particles, as well as their weight, determines the point of discharge. While various types of air classifiers could be used to carry out this step, the air'table type and, in particular, the dry table manufactured by Sutton, Steele and Steele, Inc., has been found to be very effective. The effect of moisture content was not found to be too critical. As long as the material was satisfactory for the semi-dry screening steps, it was always found satisfactory for the air classification step. The proportions, nature, size and shapes of the various components of this middle fraction did affect sharpness of the separation whenever they were varied within fairly wide limits. Thus, if there was a fairly high proportion of wood in the middle fraction, some of this wood would appear in the bark cork chip fraction. While generally it is necessary to separate the middle fraction of the semi-dry'screening steps into only two fractions, namely, a bark cork chip fraction and a fibrous fraction consisting mainly of bark fiber and wood, it is possible to operate the air table in such a way that this middle fraction is separated into several fractions. Whether or not this is done Will depend on the nature of the fraction being processed, the separation desired and the use to which these separated fractions can be put. Also, for certain barks, especially those not having a stringy-fibrous inner bark (e.g., Douglas Fir bark), the semi-dry screening steps may be omitted and the required separation made directly on an air table.

The wet disintegration of the fibrous fraction made up of the bark fiber-wood fraction from the air-classification step and the rejected fibrous fraction from the first semidry screening step, has as'its purpose the disintegration, fiberization or pulping of the bark fiber in such a way that the woody component of this combined fraction is not reduced in size in any substantial way. To achieve this objective, several types of conventional disintegrating or refining equipment can be used. It has been found that the use of disk attrition mills are very effective. In particular, the most effective type of disk mill has been that type equipped with a peripheral control ring. For example, by operating a Sprout, Waldron and Company 36-2 disk refiner with flat plates fixedat a coarse setting, the control ring setting can be varied to give a wide range of bark pulps without refining the woody component to any appreciable extent. The power per ton of feed required for the desired disintegration has been found to be low. Water should be added to the combined fraction prior to disintegration until the moisture content is above approximately 85%. A 95% moisture figure has been found to be satisfactory in practice. Moisture contents as high as 99% and over can be used, but no commensurate advantage is obtained above this amount.

The wet screening of this disintegrated combined fraction has as its objective the separation of the disintegrated bark fiber fraction (or bark pulp) from the wood fraction. For wet screening a moisture content of 98% or more is desirable, since the pulp consistency in conventional wet screening is usually from 1.5 to 0.3%. Moisture contents of 98% to 99.7% can be used in the wet screening step. Higher moisture contents are usable but no commensurate advantage is obtained.

The wood fraction and bark fiber fraction constitute, 1

respectively, products 1 and 2 mentioned above. The main reason for making the separation into these two fractions is that the energy requirements for reducing the wood fraction to a usable pulp are many times that required for reducing the bark fiber fraction to a usable pulp. Thus, if an attempt were made to reduce the wood fraction to pulp before it was separated from the bark fiber fraction, the net result would be that the bark fiber would be reduced to a completely disintegrated mass of material unusable as a pulp. On the other hand, if the combined fraction could be used without such a separation, both the disintegration and wet screening steps could be omitted.

Conventional equipment can be used to achieve this wet screening objective. The actual type used and its method of operation will depend somewhat on the nature of the disintegrated combined fraction. For example, if the proportion of wood is not much over 25%, then a conventional centrifugal pulp screen can be used; if it is much higher, a knotter or sliver screen can be used, e.g., the revolving screen-plate type or the vibrating type of which the Jonsson Knotter Screen manufactured by Bird Machine Co. is a specific example. Specifications as to screen size will depend somewhat on the degree of disintegration given to the combined fraction and other factors; in most cases, when using the centrifugal pulp screen those sizes used in secondary screening operations will be found satisfactory.

Depending on the nature of the barking waste, the type of equipment used in the several operational steps mentioned above and in the type of product required, it may be necessary to purify or clean the bark fiber product. To do this, various known methods can be ,used. However, we have found that if it is necessary to remove wood particles, commonly referred to as wood seeds and any remaining bark cork which has passed through the screens, then this can be done very effectively in equipment commonly referred to as centrifugal wet separators and, in particular, those of the pressure-drop type.

Having described the various operational steps of our invention, we will now illustrate the invention further by the following examples (product numbers refer to the products listed above):

Example 1 The barking waste discussed below is that from the early part of the barking season.

A mixture of spruce and balsam logs containing a small percentage of hemlock and poplar logs was debarked in a drum barker. The drum barker waste was broken up and dewatered in a Stacomizer (trademark of Stacom Industries, Inc.) to an average moisture content of 68% by weight and fed into a 36" single-runner disk attrition mill equipped with spike-tooth plates. The bark was then conveyed into a trommel which had a diameter of 18", a length of 6' and consisted of a screen having openings of A square. The inclination of the trommel was 2 per foot, the speed 60 r.p.m. The screen was kept clean by means of air jets. The material rejected by the trommel represented 62% by weight of the total bark fed to the trommel (on an oven-dry basis) and had a moisture content of 70%. This fraction contained 82% fibrous inner bark, 11% wood particles and 7% outer bark which also appeared to be mainly fibrous in structure.

The material accepted by the trommel represented 38% by weight on an oven dry basis and had a moisture content of 63 This fraction was further separated over an 8-mesh vibrating screen into an accepted fines fraction (product 4) representing 15% by weight of the total amount of bark, and a rejected fraction representing 23% by weight of the total amount of bark. The fines consisted of scaly outermost bark, bark and wood debris, and dust.

The fraction that was rejected by the vibrating screen was separated by means of a Sutton, Steele and Steele dry table into a cork-like chip fraction (product 3), representing 8% by weight of the total bark, and a fibrous fraction representing 15 by weight of the total amount of bark. The fibrous fraction of the air float separator was combined with the fibrous fraction from the trommel to give a total yield of fibrous material of 77% by weight of the total amount of bark.

The combined fibrous fraction was pulped in a single disk (SW 362) refiner manufactured by Sprout Waldron Inc. and equipped with plate pattern Nos. 16,808, 16,8081. Energy consumption in this stage was 7.6 H.P.d./ADT (Horsepower days per air dry ton of pulp); the refining consistency was 6% and the plate clearance 0.075 inch. Under these conditions, little or no work was done on the wood present with the bark, but at the same time the bark fiber was reduced to fiber dimensions.

The refined material was diluted to approximately 1% and screened in a small centrifugal rotary screen manufactured by Bitter-Jung equipped with 0.104 inch perforated screen-plate. In the rotary screening stage approximately 7% of the original total bark was rejected as coarse wood particles (product 1); the 70% (of the total bark) accepted by the screen, consisted mainly of bark fibers pulp (product 2).

The above bark pulp, product 2, was used in conjunction with the wood material, product 1, to make insulating board. To do this, the following further steps were undertaken: the wood material, product 1, was fiberized in a disk refiner into a high-freeness wood pulp (if insufficient wood pulp were available, other waste wood, e.g., wood shavings, could be fiberized along with product 1); the bark pulp was put through a 610 Vorject (trademark of Nichols Engineering and Research Corporation) centrifugal separators or cleaner to remove the wood seeds and any residual bark cork; the accepted bark pulp from the cleaner was then passed over a screen to remove the very fine bark material or debris, thereby converting it into a higher freeness bark pulp; the higher freeness bark pulp was blended in the proper proportions with the high-freeness wood pulp and this mixed furnish was used to make insulating board.

Example 2 The barking waste discussed here is from the latter part of the barking season. To follow this illustration, the following figures should be substituted in Example 1 above: The material rejected by the trommel represented 36% of the total bark fed to the trommel, the material accepted by the trommel representing 64%; the accepted fines fraction (from the vibrating screen) representing 17% (product 4), the rejected fraction representing 47%; the cork-like chip fraction (from the air float separator) represented 10% (product 3), and a fibrous fraction represented 37%; the combined fibrous material was 73%.

In the refining of this combined fraction, plate pattern Nos. 17591 and 17591A were used in the Sprout Waldron, 36-2 single disk refiner, the energy consumption Example 3 The following example illustrates the use of two vibrating screen stages in place of the arrangement in the above examples where one vibrating screen was used in series with a trommel.

Barking waste very similar to that used in Example 1 was broken up and dewatered in a Stacom press and fed into a single-runner, disk attrition mill equipped with size reduction of said fibrous components, thereafter semidry screening said barking waste to yield a coarse stringy fibrous product which is rejected by said screening and a less coarse residue which is passed by said screening, and

thereafter further semi-dry screening said less coarse residue to yield a coarse product containing wood fiber, bark fibrous material and bark cork chips, and a less coarse product containing finely comminuted material of wood,

. bark fiber, bark cork and scale.

spike-tooth plates. This bark was then fed over a vibrating screen equipped with a 4-mesh screen; the accepted fraction amount to 35% of the total bark and rejected coarse fibrous fraction amounted to 65%. The accepted fraction was further separated on a vibrating screen equipped with an 8-mesh screen; the accepted fraction amounted to 13% and the rejected fraction to 22% of the total bark fed to the first vibrating screen.

The above description and examples are intended to be illustrative only. Any modification or variation therefrom which conforms to the spirit of our invention is intended to be included within the scope of the claims. For example, a further variation would be to omit the second semi-dry screening step and to air-classify the accepted fraction from the first semi-dry screening step to yield a bark product consisting mainly of bark cork chips and a fraction consisting of the residue of this accepted fraction (from the first semi-dry screening step). If desired, this residue may be, itself, subjected to either a further air classification and/or to a semi-dry screening step.

What is claimed is:

1. Process for treating barking waste which contains a fibrous bark component and a fibrous wood component comprising the steps of disassociating said waste at a moisture content of at least about 85% based on the wet weight of said waste, wherein said bark component is considerably reduced in size and said wood component is not substantially reduced in size, and wet screening the resulting mixture at a moisture content of at least about 98% to separate said wood component from said bark component.

2. A process for the treatment of barking waste of the type having a stringy fibrous component and a non-fibrous component, comprising dewatering and disintegrating said barking waste so that-the moisture content thereof is below 75% and above 30% of the wet weight of said waste and the individual pieces are no longer than one foot in their maximum dimension, thereafter disassociating said fibrous and non-fibrous components and further disintegration of said non-fibrous component to separate said non-fibrous and fibrous components thereof from one another to the extent that each is capable of moving independently of the other except for physical entanglement with minimum reduction in length of said fibrous component, and thereafter semi-dry screening said waste to yield a coarse stringy fibrous product which is rejected by the screening and a less coarse residue which is passed by the screening.

3. A process for the treatment of barking waste of the type having a stringy fibrous component and a non-fibrous component, comprising dewatering and disintegrating said barking waste so that the moisture content thereof is below 75% and above 30% of the wet weight of said waste and the individual pieces are no longer than one foot in their maximum dimension, thereafter disassociating said waste to separate the non-fibrous and fibrous components thereof from one another to the extent that each is capable of moving independently of the other except for physical entanglement and in the substantial absence of 4. A process for the treatment of barking waste of the type having a stringy fibrous component and a non-fibrous component comprising a dewatering and coarse disintegration of the barking waste so that the moisture content is below and above 30% of the wet weight of the barking waste, a further disintegration of the deiwatered and coarsely disintegrated barking waste in order to loosen the non-fibrous bark component from the fibrous bark component so that each component is capable of moving independently of the other except for physical entanglement, said further disintegration being such that the stringy fibrous bark component is shredded into as long and stringy a structure as possible, a semi-dry screening of the further disintegrated barking waste to yield a coarse fibrous fraction consisting of stringy fibrous bark and a less coarse fraction consisting of particles of Wood, bark fiber and bark scale, addition of Water to the coarse fibrous fraction until the moisture content is of the wet weight thereof, wet disintegration of the coarse fibrous fraction wherein the bark fiber is substantially reduced in size, and wet screening of the disintegrated coarse fibrous fraction to yield a wood product consisting of particles of wood and wood fiber and a bark product consisting primarily of bark fiber.

5. A process for the treatment of barking Waste of the type having a fibrous component and a nonafibrous component, comprising a dewatering and coarse disintegration of the barking waste so that the moisture content of the barking waste is below 75 and above 20% of the wet weight of the barking waste and the individual pieces are e no longer than 1 foot in their maximum dimension, a further disintegration of the waste whereby the nonfibrous and fibrous fractions of the bark are separated from one another to the extent that each is capable of moving independently of the other except for physical entanglement, said fibrous fraction being shredded but substantially unreduced in length by said further disinte-' gration, a semi-dry screening of the barking Waste to yield a coarse fibrous fraction and a less coarse fraction,

fibrous and fibrous fractions of the bark are separated from one another to the extent that each is capable of moving independently of the other except for physical entanglement, said fibrous fraction being shredded but substantially unreduced in length by said further disintegration, a semi-dry screening of the barking waste to yield a fines product and a residue, and air classification 3f said residue to yield a cork product and a fibrous resi- 7. A process for the treatment of barking waste of the type having a fibrous component and a non-fibrous component, comprising a dewatering and coarse disintegration of the barking waste so that the moisture content of the barking waste is below 75% and above 20% of the wet weight of the barking waste and the individual pieces are no longer than 1 foot in their maximum dimension, a further disintegration of the waste l; l whereby the non-fibrous and fibrous fractions of the bark are separated from one another to the extent that each is capable of moving independently of the other except for physical entanglement, said fibrous fraction being shredded but substantially unreduced in length by said further disintegration, a first semi-dry screening of the barking waste to yield a coarse fibrous fraction and a less coarse fraction, a second semi-dry screening of the said less coarse fraction of the barking waste to yield a fine product and a middle fraction, and an air classification of said middle fraction to yield a cork product and a fibrous residue.

8. A process for the treatment of barking waste of the type having a fibrous component and a non-fibrous component, comprising a dewatering and coarse disintegration of the barking waste, a further disintegration of the waste whereby the non-fibrous and fibrous fractions of the bark are separated from one another to the extent that each is capable of moving independently of the other except for physical entanglement, said fibrous fraction being shredded but substantially unreduced in length by said further disintegration, a first semi-dry screening of the barking waste to yield a coarse fibrous fraction and a less coarse fraction, a second semi-dry screening of the said less coarse fraction of the barking waste to yield a fines product and a middle portion, air classification of said middle portion to yield a cork product and a fibrous residue, addition of water to the coarse fibrous fraction and the fibrous residue, wet disintegration of the said coarse fibrous fraction and said fibrous residue to produce a further fibrous portion wherein'the bark fiber pieces are reduced considerably in size whereas the wood pieces are not substantially reduced in size, and a wet screening of the further fibrous fraction to yield a wood product and a bark fiber product.

9. A process as claimed in claim 8, wherein the dewatering and coarse disintegration of the barking waste reduces its moisture to a value below 75% and above of the wet weight of the barking waste.

10. A process as claimed in claim 9, wherein the moisture content of the coarse fibrous fraction and the fibrous residue is at least 85% of the wet weight of the coarse fibrous fraction and the fibrous residue prior to the wet disintegration step.

11. A process as claimed in claim 10, wherein it the moisture content of the further fibrous fraction is less than 98.5% of the wet weight of the further fibrous fraction, water is added prior to the wet screening step to make the moisture content of the further fibrous fraction between 98.5 and 99.7% of the wet weight of the further fibrous fraction.

12. A process for the treatment of barking waste of the type having a fibrous component and a non-fibrous component and having a moisture content between 75% and 20% of the wet weight of the barking waste and wherein the individual pieces of barking waste are no longer than 1 foot in their maximum dimension and wherein the non-fibrous and fibrous fractions of the bark are separated from one another to the extent that each is capable of moving independently of one another except for physical entaglement, comprising a semi-dry screening of the barking waste to yield a coarse fibrous fraction and a less coarse fraction, air classification of said less coarse fraction to yield a cork product and a fibrous residue, addition of water to the coarse fibrous fraction and to the fibrous residue until the moisture content is at least 85% of the wet weight of the coarse fibrous fraction and fibrous residue, wet disintegration of said coarse fibrous fraction and said fibrous residue to produce a further combined fibrous fraction wherein the bark fiber pieces are reduced considerably in size whereas the wood pieces are not substantially reduced in size, addition of water to the combined fraction if the moisture content thereof is less than 98% of the wet weight thereof until the moisture content of the combined fraction is at least 98% of the wet weight of the combined fraction, and a wet screening of the combined fraction to yield a wood product and a bark fiber product.

13. A process for the treatment of barking waste of the type having a fibrous component and a non-fibrous component, comprising a dewatering and disintegration of the barking waste so that the moisture content of the barking waste is below and above 20% of the wet weight of the barking waste and the individual pieces are no longer than 1 foot in their maximum dimension and the non-fibrous and fibrous fraction of the bark are separated from one another to the extent that each one is capable of moving independently of the other except for physical entanglement, a semi-dry screening of the barking waste to yield a coarse fibrous fraction and a less coarse fraction, air classification of said less coarse fraction to yield a cork product and a fibrous residue, addition of water to the coarse fibrous fraction and the fibrous residue until the moisture content is at least of the wet weight of the coarse fibrous fraction and fibrous residue, wet disintegration of said coarse fibrous fraction and said fibrous residue to produce a further combined fibrous fraction wherein the bark fibrous pieces are reduced considerably in size whereas the wood pieces are not substantially reduced in size, addition of water to the combined fraction if the moisture content thereof is less than 98% of the wet weight thereof until the moisture content of the combined fraction is at least 98% of the wet weight of the combined fraction, and a wet screening of the combined fraction to yield a wood product and a bark fiber product.

14. A process for the treatment of barking waste of the type having a fibrous component and a non-fibrous component, comprising a rewatering and coarse disintegration of the barking waste so that the moisture content of the barking waste is below 75 and above 20% of the wet weight of the barking waste and the individual pieces are no longer than 1 foot in their maximum dimension, a further distintegration of the waste whereby the non-fibrous and fibrous fractions of the bark are separated from one another to the extent that each is capable of moving independently of the other except for physical entanglement, said fibrous fraction being shredded but substantially unreduced in length by said further disintegration, a semi-dry screening of the barking waste to yield a coarse fibrous fraction and a less coarse fraction, air classification of said less coarse fraction to yield a cork product and a fibrous residue, addition of water to the coarse fibrous fraction and to the fibrous residue until the moisture content is at least 85 of the wet weight of the coarse fibrous fraction and fibrous residue, wet disintegration of said coarse fibrous fraction and said fibrous residue to produce a further combined fibrous fraction wherein the bark fiberpieces are reduced considerably in size whereas the wood pieces are not substantially reduced in size, addition of water to the combined fraction if the moisture content thereof is less than 98% of the wet weight thereof until the moisture content of the combined fraction is at least 98% of the wet weight of the combined fraction, and a wet screening of the combined fraction to yield a wood product and a bark fiber product.

15. A process for the treatment of barking waste of the type having a fibrous component and a non-fibrous component and having a moisture content between 75 and 20% of the wet weight of the barking waste and wherein the individual pieces of waste are no longer than 1 foot in their maximum dimension and wherein the non-fibrous and fibrous fractions of the bark are separated from one another to the extent that each is capable of moving independently of the other except for physical entanglement, comprising a semi-dry screening of the barking waste to yield a fines product and a residue, an air classification of the residue to yield a cork product and a fibrous residue, addition of water to said fibrous residue until the moisture content is at least 85% of the Wet weight of said fibrous residue, wet disintegration of said fibrous residue to produce a further fibrous fraction wherein the bark fiber pieces are reduced considerably in size whereas the Wood pieces are not substantially reduced in size, addition of water to the further fibrous fraction if the moisture content thereof is less than 98% of the wet Weight thereof until the moisture content of the further fibrous fraction is at least 98% of the wet weight of the further fibrous fraction, and a wet screening of the further fibrous fraction to yield a wood product and a bark fiber product.

16. A process for the treatment of the barking waste of the type having a fibrous component and a non-fibrous component, comprising a dewatering and disintegration of the barking waste so that moisture content of the barking Waste is below 75% and above 20% of the wet weight of the barking waste and the individual pieces are no longer than 1 foot in their maximum dimension and the non-fibrous and fibrous fractions of the bark are separated from one another to the extent that each is capable of moving independently of the other except for physical entanglement, a semi-dry screening of the barking waste to yield a fines product and a residue, air classification of said residue to yield a cork product and a fibrous residue, addition of water to said fibrous residue until the moisture content is at least 85% of the Wet weight of said fibrous residue, wet disintegration of said fibrous residue to produce a further fiber fraction wherein the bark fiber pieces are reduced considerably in size whereas the wood pieces are not substantially reduced in size, addition of water to the further fibrous fraction if the moisture content thereof is less than 98% of the wet weight thereof until the moisture content of the further fibrous fraction is at least 98% of the wet weight of the further fibrous fraction and wet screening the further fibrous fraction to yield a wood product and bark fiber product.

17. A process for the treatment of barking waste of the type having a fibrous component and a non-fibrous component, comprising a dewatering and coarse disintegration of the barking waste so that the moisture content of the barking waste is below 75% and above 20% of the wet waste of the barking waste and the individual pieces are no longer than 1 foot in their maximum dimension, a further disintegration of the waste whereby the non-fibrous and fibrous fractions of the bark are separated from one another to the extent that each is capable of moving independently of the other except for physical entanglement, said fibrous fraction being shredded but substantially unreduced in length by said further disintegration, a semi-dry screening of the barking waste to yield a fines'product and a residue, air classification of said residue to yield a cork product and a fibrous residue, addition of water to said fibrous residue until the moisture content is at least 85% of said fibrous residue, wet disintegration of said fibrous residue to produce a further fibrous fraction wherein the bark fiber pieces are reduced considerably in size whereas the wood pieces are not substantially reduced in size, addition of water to the further fibrous fraction if the moisture content thereof is less than 98% of the wet weight thereof until the moisture content of the further fibrous fraction is at least 98% of the wet weight of the further fibrous fraction, and wet screening the further fibrous fraction to yield a Wood product and a bark fiber product.

18. A process for the treatment of barking waste of the type having a fibrous component and a non-fibrous component and having a moisture content between 75 and 20% of the wet weight of the barking waste and wherein the individual pieces of barking waste are no longer than 1 foot in their maximum dimension and wherein the non-fibrous and fibrous fractions of the bark are separated from one another to the extent that each is capable of moving independently of the other except for physical entanglement, comprising a first semi-dry screening of the barking waste to yield a coarse fibrous fraction and a less coarse fraction, a second semi-dry screening of the less coarse fraction to yield a fines product and a middle fraction, air classification of said middle fraction to yield a cork product and a fibrous residue, addition of water to the coarse fibrous fraction and the fibrous residue until the moisture content is at least of the wet weight of the coarse fibrous fraction and fibrous residue, wet disintegration of the said coarse fibrous fraction and said fibrous residue to produce a further combined fibrous fraction wherein the bark fiber pieces are reduced considerably in size whereas the wood pieces are not substantially reduced in size, addition of water to the further fibrous fraction if the moisture content thereof is less than 98% of the wet weight thereof until the moisture content of the further fibrous fraction is at least 98% of the wet Weight of the further fibrous fraction, and a wet screening of the further fibrous fraction to yield a wood product and a bark fiber product.

19. A process for the treatment of barking waste of the type having a fibrous component and a non-fibrous component, comprising a dewatering and disintegration of the barking waste so that the moisture content of the barking waste is below 75 and above 20% of the wet waste of the barking waste and the individual pieces are no longer than 1 foot in their maximum dimension and the non-fibrous and fibrous fraction of the bark are separated from one another to the extent that each is capable of moving independently of the other except for physical entanglement, a first semi-dry screening of the barking Waste to yield a coarse fibrous fraction and a less coarse fraction, a second semi-dry screening of the soil less coarse fraction of the barking waste to yield a fines product and a middle fraction, air classification of said middle fraction to yield a cork product and a fibrous residue, addition of Water to the coarse fibrous fraction and the fibrous residue until the moisture content is at least 85 of the Wet weight of the coarse fibrous fraction and fibrous residue, wet disintegration of the said coarse fibrous fraction and said fibrous residue to produce a further fibrous fraction wherein the bark fiber pieces are reduced considerably in size whereas the wood pieces are not substantially reduced in size, addition of Water to the further fibrous fraction if the moisture content thereof is less than 98% of the wet Weight thereof until the moisture content of the further fibrous fraction is at least 98% of the wet weight of the further fibrous fraction, and wet screening of the further fibrous fraction to yield a wood product and a bark fiber product.

20. A process for the treatment of barking waste of the type having a fibrous component and a non-fibrous component, comprising a dewatering and coarse disintegration of the barking waste so that the moisture content of the barking waste is below 75 and above 20% of the wet weight of the barking waste and the individual pieces are no longer than 1 foot in their maximum dimension, a further disintegration of the waste whereby the non-fibrous and fibrous fractions of the bark are separated from one another to the extent that each is capable of moving independently of the other except for physical entanglement, said fibrous fraction being shredded but substantially unreduced in length by said further disintegration, a first semi-dry screening of the barking waste to yield a coarse fibrous fraction and a less coarse fraction, a second semi-dry screening of the said less coarse fraction of the barking Waste to yield a fines product and a middle fraction, and air classification of said middle fraction to yield a cork product and a fibrous residue, addition of water to said fibrous residue and coarse fibrous fraction until the moisture content thereof is at least 85%, wet disintegration of the said fibrous residue and coarse fibrous fraction to produce a further combined fibrous fraction wherein the bark fiber pieces are reduced considerably in size whereas the wood pieces are not sub stantially reduced in size, addition of water to the further 1 5 fibrous fraction if the moisture content thereof is less than 98% of the Wet Weight thereof until the moisture content of the further fibrous fraction is at least 98% of the wet Weight thereof, and wet screening the further fibrous fraction to yield a Wood product and a bark fiber product.

References Cited by the Examiner UNITED STATES PATENTS 1,797,901 3/1931 Darling 24128 X 18 Collins 24128 X Heritage 241-28 X Heritage et al 241-24 Eberhardt 241--28 X Owens 241-14 X Blanchard 241--14 Vroom 241-24 LESTER M. SWINGLE, Primary Examiner.

3 /1943 Anway 41 1O HARRY F. PEPPER, JR., Assistant Examiner. 

2. A PROCESS FOR THE TREATMENT OF BARKING WASTE OF THE TYPE HAVING A STRINGY FIBROUS COMPONENT AND A NON-FIBROUS COMPONENT, COMPRISING DEWATERING AND DISINTEGRATING SAID BARKING WASTE SO THAT THE MOISTURE CONTENT THEREOF IS BELOW 75% AND ABOVE 30% OF THE WET WEIGHT OF SAID WASTE AND THE INDIVIDUAL PIECES ARE NO LONGER THAN ONE FOOT IN THEIR MAXIMUM DIMENSION, THEREAFTER DISASSOCIATING SAID FIBROUS AND NON-FIBROUS COMPONENT AND FURTHER DISINTEGRATION OF SAID NON-FIBROUS COMPONENT TO SEPARATE SAID NON-FIBROUS AND FIBROUS COMPONENTS THEREOF FROM ONE ANOTHER TO THE EXTENT THAT EACH IS CAPABLE OF MOVING INDEPENDENTLY OF THE OTHER EXCEPT FOR PHYSICAL ENTANGLEMENT WITH MINIMUM REDUCTION IN LENGTH OF SAID FIBROUS COMPONENT, AND THEREAFTER SEMI-DRY SCREENING SAID WASTE TO YIELD A COARSE STRINGY FIBROUS PRODUCT WHICH IS REJECTED BY THE SCREENING AND A LESS COARSE RESIDUE WHICH IS PASSED BY THE SCREEENING. 